Mercury (II) Ion Sensing Through in Situ Synthesis of Gold Nanoparticles

Divalent mercury ion (Hg²⁺) is a highly toxic substance that significantly impairs the central nervous system and genetic functions. While numerous colorimetric methods have been developed for rapid Hg²⁺ detection in environmental samples, many existing sensing strategies involve complex processes such as nanostructure/substrate fabrication, recognizer modification, purification steps, or the use of fluorescent measurements. Here, we present a simplified one-pot Hg²⁺ assay, termed MiDAS (mercury-induced direct AuNP synthesis), utilizing only pyruvate (Pyr) and UV light. The method establishes Hg²⁺ sensing through in situ synthesis of gold nanoparticles (AuNPs). In this mechanism, Pyr selectively chelates Hg²⁺ and functions as an effective reducing agent, converting Au³⁺ to AuNPs and inducing significant optical changes in samples, which was corroborated by density functional theory calculations. The developed assay exhibited high specificity for Hg²⁺ and generated quantitative signals at concentrations as low as 32 pM [Hg²⁺]. The potential for on-site application of MiDAS was demonstrated through the detection of spiked Hg²⁺ in tap water, river water, and canned tuna samples.